In order to minimize the space required for electronic components used in mobile products, such as mobile communication devices and wearable devices, a multi-die system in package (SiP) may be used. In a SiP package, multiple active electronic components with different functionalities may be included within a single package. For example, active electronic components may include one or more semiconductive dies with integrated circuitry, such as transistors, diodes, or the like. A SiP may also include one or more passive electronic components, such as resistors, capacitors, integrated passive devices (IPDs) or the like. Often, the entity that assembles the SiP does not produce each of the electrical components that are integrated into the SiP. Electronic components that are obtained from an outside source are typically received pre-packaged. These pre-packaged components may not be suitable for integration into a SiP when certain packaging processes are used.
For example, a SiP may be formed with an embedded wafer level ball grid array (e-WLB) or an embedded panel level ball grid array (e-PLB) processes. In such packages, a mold layer is formed around a plurality of active and passive electrical components to form a reconstituted wafer or a reconstituted panel. A redistribution layer may then be formed over the surface of the mold layer to allow interconnects to the terminals to fan-out beyond the edges of the electrical component. In e-WLB and e-PLB packages, the electronic components typically utilize gold, aluminum, or copper terminals.
However, it is not always possible to obtain the desired electrical component with copper, aluminum, or gold terminals when components are received pre-packaged from an outside source. Instead, pre-packaged electronic components may include solderable terminals, such as solder balls. The use of solderable materials, such as tin-based solders, may reduce the reliability of the SiP. The reduction in the reliability of the device may result from the formation of intermetallic compounds (IMCs) at the solderable terminal. For example, during high temperature operations where a redistribution layer, such as a copper redistribution layer, is in contact with a solderable terminal, the copper may diffuse into the solder and produce IMCs. The volume of the IMCs is lower than the volume of the solder and may produce voids within the terminal or cause the terminal to crack. Additionally, the volume of solder materials will increase during reflow operations by a low-single-digit percentage value of the original volume. This increase in volume will cause the package to crack when the solder terminal is embedded within a mold layer, unless there is excellent adhesion between the solder material and the mold layer.